Without limiting the scope of the present invention, its background will be described in relation to fracpack and gravel pack systems for use in completing wellbores in open hole subterranean hydrocarbon bearing formations, as an example.
Fracpacks and gravel packs are commonly performed during the completion of oil and gas wells. During these operations, a completion string including one or more sand control screens is typically run downhole and positioned adjacent to the production interval. A service tool is positioned inside of the completion string to provide a conduit for pumping fluids downhole.
In general, the fracpack operation is used to stimulate well production by pumping liquid under high pressure down the well into the reservoir rock adjacent to the wellbore to create fractures therein. Propping agents or proppants suspended in the high-pressure fluids are used to keep the fractures open, thus facilitating increased flow into the wellbore. In addition, the proppants fill the annulus between the screens and the casing to provide a first layer of filtration, which restricts formation sand migration. The gravel pack operation is commonly used in unconsolidated or loosely consolidated reservoirs for sand control. The gravel pack slurry is pumped down the well into the annulus between the screens and the casing while taking fluid returns to the surface, thereby minimizing fluid loss into the formation. The gravel pack provides a packed sand layer in the wellbore, which restricts formation sand migration.
It has been found, however, that for certain completions, installation of casing and the associated cementing process may be undesirable. For example, in deepwater wells, it may be preferable to complete the wells open hole. One reason for this preference is the risk of experiencing a problem in a cased hole completion that requires the completion to be abandoned. In such a situation, an alternative wellbore may be sidetracked from the existing cased hole wellbore, however, the subsequent wellbore must be completed using smaller diameter equipment. This reduction in hole size not only limits production capabilities but also diminishes the ability to perform desired treatment operations, such as fracpack operations, as the service tool ratings for the smaller diameter tools limits the flow rates and proppants volumes that can be delivered. One way to avoid this problem and to maintain the larger hole size even when a sidetrack is required, is by completing the wells open hole.
It has been found, however, the certain problems arises when gravel packing or fracpacking in open hole environments. For example, when the gravel pack or fracpack slurry is pumped out of the crossover assembly and the closing sleeve, the slurry immediately come in contact with the formation. As the slurry is commonly injected at a location uphole of the particular zone of interest, the liquid portion of the slurry may leak off into an undesired portion of the formation, which dehydrates the slurry and may cause sand bridges to form in the wellbore. These sand bridges not only result in a failed pack but may also cause the service tool to become stuck within the completion string if the slurry dehydration takes place proximate to and inside the closing sleeve.
Therefore, a need has arisen for a system and method of completing open hole wells. A need has also arisen for such a system and method that allows for formation stimulation and sand control in open hole completions. Further, need has arisen for such a system and method that prevents slurry dehydration proximate to and inside the closing sleeve during such treatment operations.